It is known that an exactly metered feeding of the quantity of binder to be added to a specific amount of wood chips or the like is decisive for the quality of the panels to be manufactured. To attain this objective, continuously operating metering devices have been developed for gluing machines, which operate with metering scales feeding constant amounts of chips in a batchwise manner per time unit, wherein either the thus-conveyed weight of the chips, with a constant belt speed, is solely adapted to the required output, or wherein the belt-type scales merely serve for registering an incoming stream of chips. In other words, it is known that there is a dependency between the output of the chip conveyor unit, on the one hand, and the binder metering pump, on the other hand. It is desirable to provide that the quantitative ratio of chips and glue generally remains constant as seen over a long period of time (DAS [German Published Application] No. 1,195,940, column 1).
To solve this well-known problem, a controllable mechanical coupling of the drive of the endless scale belt with the drive mechanism for the binder metering pump has been provided when using a metering tank for the dry chips, a belt scale, and a binder metering pump, wherein the outputs of the belt scale and the binder metering pump are dependent on each other.
In spite of the desire to take care that the quantitative ratio of chips and glue remain constant, this objective cannot be attained by means of the above directions, because difficulties can occur in several kinds of chips in maintaining the weight-wise delivery of the chips at a constant value at all times. Consequently, a secondary control procedure is necessary, which is achieved by exerting a corresponding effect on the binder metering pump. However, such a secondary control is undesirable, because this complicates the structure of the metering device. The invention starts with the consideration that the solutions heretofore provided for a satisfactory metering procedure strove to maintain the quantitative ratio of chips and glue generally at a constant value over a long period of time, and that consequently the glue output had to be adapted to the amount of chips delivered. As a result, on account of this secondary control, the amount of chips present in the gluing machine will, at one time, be provided with an excessive amount of glue and, at another time, be supplied with an insufficient amount of glue (DOS [German Unexamined Laid-Open Application] No. 2,138,082, second paragraph on page 3).